[austinhyde]

If by "webapp wrapper" you actually mean a site-specific browser, there's Fluid: http://fluidapp.com/

Or, if you mean an SDK or framework for writing a native app using web technologies, I know of a few:

TideSDK: http://www.tidesdk.org/

AppJS, if you're not opposed to Node.js: http://appjs.org

Awesomium: http://awesomium.com/